python thread-condition()简单示例

#!/usr/bin/env python
# -*-coding:utf-8-*-


import threading
import time

condition = threading.Condition()
products = 0


class Producer(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        global condition, products
        while True:
            if condition.acquire():
                if products < 10:
                    products += 1
                    print("Producer(%s):deliver one, now products:%s" % (self.name, products))
                    condition.notify()
                else:
                    print ("Producer(%s):already 10, stop deliver, now products:%s" %(self.name, products))
                    condition.wait()
                condition.release()
                time.sleep(2)


class Consumer(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        global condition, products
        while True:
            if condition.acquire():
                if products > 1:
                    products -= 1
                    print("Consumer(%s):consume one, now products:%s" % (self.name, products))
                    condition.notify()
                else:
                    print("Consumer(%s):only 1, stop consume, products:%s" %(self.name, products))
                    condition.wait()
                condition.release()
                time.sleep(1)

if __name__ == "__main__":
    for q in range(0, 10):
        p = Producer()
        p.start()

    for i in range(0,2):
        c = Consumer()
        c.start()

 执行结果：

Producer(Thread-1):deliver one, now products:1
Producer(Thread-2):deliver one, now products:2
Producer(Thread-3):deliver one, now products:3
Producer(Thread-4):deliver one, now products:4
Producer(Thread-5):deliver one, now products:5
Producer(Thread-6):deliver one, now products:6
Producer(Thread-7):deliver one, now products:7
Producer(Thread-8):deliver one, now products:8
Producer(Thread-9):deliver one, now products:9
Producer(Thread-10):deliver one, now products:10
Consumer(Thread-11):consume one, now products:9
Consumer(Thread-12):consume one, now products:8
Consumer(Thread-12):consume one, now products:7
Consumer(Thread-11):consume one, now products:6
Producer(Thread-10):deliver one, now products:7
Producer(Thread-7):deliver one, now products:8
Producer(Thread-4):deliver one, now products:9
Producer(Thread-3):deliver one, now products:10
Producer(Thread-2):already 10, stop deliver, now products:10
Producer(Thread-8):already 10, stop deliver, now products:10
Producer(Thread-6):already 10, stop deliver, now products:10
Producer(Thread-9):already 10, stop deliver, now products:10
Producer(Thread-5):already 10, stop deliver, now products:10
Producer(Thread-1):already 10, stop deliver, now products:10
Consumer(Thread-11):consume one, now products:9
Consumer(Thread-12):consume one, now products:8
Consumer(Thread-11):consume one, now products:7
Consumer(Thread-12):consume one, now products:6
Producer(Thread-4):deliver one, now products:7
Producer(Thread-3):deliver one, now products:8
Producer(Thread-10):deliver one, now products:9
Producer(Thread-7):deliver one, now products:10
Producer(Thread-2):already 10, stop deliver, now products:10
Producer(Thread-8):already 10, stop deliver, now products:10
Consumer(Thread-12):consume one, now products:9
Consumer(Thread-11):consume one, now products:8
Producer(Thread-9):deliver one, now products:9
Producer(Thread-6):deliver one, now products:10
Consumer(Thread-11):consume one, now products:9
Consumer(Thread-12):consume one, now products:8
Producer(Thread-3):deliver one, now products:9
Producer(Thread-1):deliver one, now products:10
Producer(Thread-10):already 10, stop deliver, now products:10
Producer(Thread-5):already 10, stop deliver, now products:10
Producer(Thread-7):already 10, stop deliver, now products:10
Producer(Thread-4):already 10, stop deliver, now products:10
Producer(Thread-8):already 10, stop deliver, now products:10
Producer(Thread-2):already 10, stop deliver, now products:10
Consumer(Thread-12):consume one, now products:9
Consumer(Thread-11):consume one, now products:8
Producer(Thread-6):deliver one, now products:9
Producer(Thread-9):deliver one, now products:10
Consumer(Thread-12):consume one, now products:9
Consumer(Thread-11):consume one, now products:8
......

Condition类：条件变量对象能让一个线程停下来，等待其它线程满足了某个“条件”。如，状态的改变或值的改变。

• acquire 　　给线程上锁 
• wait           wait方法释放当前线程占用的锁，同时挂起线程，直至被唤醒或超时（需timeout参数）。当线程被唤醒并重新占有锁的时候，程序才会继续执行下去。
• notify　　   唤醒一个挂起的线程（如果存在挂起的线程）。注：notify()方法不会释放所占用的锁。
• notifyall　　调用这个方法将通知等待池中所有线程，这些线程都将进入锁定池尝试获得锁定。此方法不会释放锁定。使用前线程必须已获得锁定，否则将抛出异常。

　　比较经典的例子是下面这个生产者与消费者的例子，这个例子网上一搜到处都是，这里简单解释一下这段代码的意义，代码中写了两个类，Consumer和Producer，分别继承了Thread类，我们分别初始化这两个类获得了c和p对象，并启动这两个线程。则这两个线程去执行run方法（这里与Thread类内部的调度有关），定义了producer全局变量和condition对象为全局变量，当producer不大于1时，消费者线程被condition对象阻塞，不能继续消费（这里是不再递减），当producer不小于10时，生产者线程被condition对象阻塞，不再生产（这里是不再累加）.